The proposed research includes studies on the development and organization of the vertebrate visual system, with emphasis on the retina. The proposal encompasses the following projects: 1) An ultrastructural study of synaptogenesis in human cones. 2) A study of the photoreceptor-pigment epithelial cell relationship in the mammalian retina. 3) The development of cat cones and the pigment epithelial sheath which contacts cone outer segments. 4) The effect of vitamin A deficiency on ground squirrel cones. A determination of the extent of degneration that occurs in cones during deficiency and the ability of degenerate cones to generate. 5) The renewal of Xenopus photoreceptor outer segments in vitro and the effect of light on this process. 6) A study of synaptic organization of the optic tectum in goldfish, including the normal tectum, after optic nerve degeneration, and after compression of the retinal project.